Google is progressively rolling out the full array of releases for Android 5.1, and the SDK is now joining the ranks. If developers open up the SDK Manager today, they will find a brand new software development kit for API 22. The SDK package is there, along with the typical documentation, samples, source code, and an assortment of system images for each of the major hardware architectures. All is ready to start updating apps to take advantage of everything Android 5.1 has to offer.

The Android ecosystem –as most of us think of it– is built on more than just an operating system and a marketplace for independent apps. It's largely shaped by dozens of services that have been built by Google, allowing developers to add rich features to their apps without building out expensive infrastructures. The Google Play services package is the core element in this equation, and it's getting a pretty major update to version 7.0 over the next couple of weeks.

The Pebble Time still has almost a month to get more pre-orders on Kickstarter, but it's already passed the $10 million mark, which is the record set by the first Pebble. In preparation for what is sure to be a big launch for the company, the new v3.0 update of Pebble's SDK is now available. Developers can start building apps for the Time, and they'll work with the regular Pebbles in the meantime.

The foldable cardboard VR kits Google gave away at I/O 2014 weren't just a one-off stunt. Today, in its developers blog, Google had some big announcements for the home-brewed virtual reality viewer.

First up, Google has grouped a handful of Cardboard-compatible apps into their own collection on the Play Store. The Cardboard app itself has also received an update, with the ability to discover cardboard apps on the Play Store, and launch them directly from the viewer.

Most of us don't want to think of Android without Google Play services. There's a good reason for that, without all of the tools Google offers, we would miss out on features like push notifications, integrated maps, and even newer things like Google Fit. Developers keep asking for more and Google is answering that call. With the latest release of Google Play services, new features are coming to Fit, Maps, Drive, And Wallet.

Developers have a lot to look forward to with the latest release of Android, but not everything requires Lollipop to run. With the official release of the SDK for API Level 21, Google also included an updated version of the AppCompat Support Library, which contains back-ported versions of UI controls and other features for use on older versions of the OS. Some of the new libraries were first available with the L Preview SDK, but just about everything has received an update, and there are some additions for the official release.

On Wednesday, Google teased developers and enthusiasts by officially announcing Lollipop, but chose to delay the release of anything substantial for another two days. Well, we've waited for the obligatory 48 hours, and the SDK is finally available, just in time for the weekend. (Yay?) Developers can finally abandon the interim SDK and move on to the real thing. There's no more pretending 'L' counts as an API Level, Android 5.0 is officially numbered 21.

Excitement over products like the Ouya, nVidia's Shield line, and even numerous gamepads proves that gaming on Android has entered the mainstream. Developers have been jumping at the opportunity to build games that work across many of the different operating systems; and thanks to the Cross-Platform SDK, they're able to integrate most of the Play Games services into their products on Windows, Mac, and Linux. Until now, this SDK has lagged behind the SDKs for Android and iOS on one specific feature: real-time multiplayer support.